In the related art, a charged particle beam apparatus configured to irradiate a predetermined position with a charged particle beam such as an ion beam or an electron beam for processing and observation is used in various fields. As the charged particle beam apparatus, there are, for example, a scanning electron microscope (SEM) which is able to irradiate with an electron beam as the charged particle beam or a focused ion beam apparatus (FIB) which is able to irradiate with a focused ion beam or the like as the charged particle beam. The scanning electron microscope allows observation of the state of a surface of a sample by detecting a secondary electron generated from the surface of the sample while scanning with the electron beam on the surface of the sample. Also, the focused ion beam apparatus allows observation of the surface of the sample by detecting the secondary electron in the same manner as the scanning electron microscope and also is able to perform etching or deposition of the sample by increasing the acceleration voltage, so that it is used for preparing samples for TEM (transmission electron microscope) or correcting photomasks. Also, in recent years, in the focused ion beam apparatus, a method of realizing a low-damage processing by using the acceleration voltage of the focused ion beam in a low-acceleration area from 100 V to 5000 V in acceleration voltage receives attention. A method for realizing a large surface processing such as wire bonding or solder bump by using the same in a heavy-current area of at least 1 nA in amount of irradiation of the focused ion beam within a range on the order of 3000 V in acceleration voltage or the like also starts to receive attention.
Incidentally, the charged particle beam apparatuses as described above include charged particle optics configured to adjust beam characteristic values, such as the focal length or the astigmatism, of the charged particle beam by electromagnetically acting on the irradiated charged particle beam in order to achieve an adequate observation or processing. In other words, the focused ion beam apparatus, for example, includes an electrostatic lens as an objective lens which causes the focused ion beam to be focused by forming an electric field by an applied voltage as the charged particle optics. Then, by setting a voltage value to be applied to the electrostatic lens as an input value, the focal length is adjusted and the focused ion beam is focused on the surface of the sample. Also, although the electrostatic lens as described above is formed to have rotational symmetry for causing the focused ion beam to be focused uniformly in the circumferential direction, the astigmatism might occur due to the fabrication in accuracy of a lens electrode and axis displacement at the time of assembly, so that the shape of the cross-section of the focused ion beam might not assume a circle. Therefore, an astigmatic correction mechanism (stigmator) configured to correct the astigmatism of the focused ion beam is used as the charged particle optics. The astigmatism correction mechanism corrects the astigmatism of the focused ion beam by forming an electric field by, for example, using two pairs of quadrupoles and setting voltage values to be applied to the respective quadrupoles as input values. The scanning electron microscope or the like is also the same in this respect and includes a magnetic field lens as the objective lens and the astigmatic correction mechanism, each forming a magnetic field which acts on the electron beam to adjust the focal length and correct the astigmatism.
In the related art, the displacement of the position of the focal point or the astigmatism as described above are adjusted and corrected specifically in the following method using the above-described charged particle optics. In other words, an image of the sample is obtained by detecting the secondary electron by irradiating the sample with the charged particle beam. Then, the direction of the astigmatism is determined from the state of the obtained image, and an input value to be inputted to an astigmatic corrector is adjusted according to the direction of the astigmatism. Furthermore, the image of the sample is obtained, and whether or not the image is in focus is determined from the state of the image, and the input value to be inputted to the objective lens is adjusted according to the state. Then, if there is further a sign of astigmatism in the obtained image, the correction of the astigmatism and the adjustment of the position of the focal point are performed again. Then, when the obtained image becomes clear without any distortion, the adjustment is completed (for example, see Non-Patent Document 1).
Also, as regards an electron beam exposure apparatus as the charged particle beam apparatus, a technology to prevent generation of variations due to an abrupt change of the input value for correcting the astigmatism when performing a linear supplement by determining optimal input values at the respective lattice points on a field according to the method as described above is disclosed (for Example, see Patent Document 1).
[Non-Patent Document 1] Fundamentals and Application of Scanning Electron Microscope, from Kyoritsu Publ. Co., Ltd., Oct. 25, 1991, pp. 80-82
[Patent Document 1] JP-A-8-83585
However, with the methods disclosed in Non-Patent Document 1 and Patent Document 1, an operator determines the state of the obtained image qualitatively and determines optimal values as input values of the respective charged particle optics. Therefore, there is a problem that a high level of performance of the operator and a great deal of time are necessary for adjusting the respective charged particle optics. Also, there arise variations in accuracy of adjustment from operator to operator, and even though the adjustment is made by the same operator, it is difficult to unify the accuracy of adjustment in different apparatuses, so that variations in performance from apparatus to apparatus may be disadvantageously resulted. In the focused ion beam apparatus as described above, since the speed of processing is fast when used in a heavy-current area, the sample might be damaged while acquiring and adjusting the image of the sample. Furthermore, since the ion beam cannot be focused effectively when being used in the heavy-current area or a low-acceleration area in comparison with the use in a low-current area and a high-acceleration area, a clear image cannot be obtained as the image of the sample for adjustment, so that the accurate adjustment cannot be achieved.